An aromatic unsaturated compound of the formula (4)
wherein Ar represents an optionally substituted aromatic group or an optionally substituted heteroaromatic group, and Y represents an electron withdrawing group (hereinafter, abbreviated as aromatic unsaturated compound (4))is useful as, for example, a synthetic intermediate of medical and agricultural chemicals or the like. For example, a compound of the following formula (7)
is known as a synthetic intermediate of fluvastatin useful as a hyperlipidemia drug as described also in, for example, WO 01/92223.
Compounds of the following formulae (8) and (9) are compounds being developed as an arteriosclerosis remedy as described also in JPH09-202775-A and JPH07-206842-A, respectively.

As a process for producing such an aromatic unsaturated compound (4), there is known, for example, a process reacting an aromatic halide with an acrylic acid compound such as acrylic acid and the like in the presence of a palladium catalyst and a base (for example, WO 01/92223), however, an aromatic halide manifesting high load on environments is required to be used as a raw material, and additionally, a hydrogen halide is by-produced together with progress of the reaction. In addition, since the above-mentioned hydrogen halide is required to be neutralized with a base, it is not necessarily a reaction of high atom economy from the standpoint of raw material.
On the other hand, as a process of higher atom economy, there is a process using a compound of the formula (1)Ar—H  (1)wherein, Ar is as defined above,as a raw material and reacting it with an acrylic acid compound. For example, there are suggested (a) a process using a ruthenium catalyst and a palladium catalyst and reacting in the presence of oxygen (for example, J. Am. Chem. Soc., 125, 1467 (2003), J. Am. Chem. Soc., 123, 337 (2001)), (b) a process using a palladium complex in an amount equal to or more than the theoretical amount (for example, J. Org. Chem., 46, 851 (1981), Heterocycles, 22, 1493 (1984)), and the like.
However, the process (a) is not necessarily advantageous from the standpoint of operation and equipments since oxygen is used and accordingly the process is required to be performed under the reaction condition not higher than the explosion limit. The process (b) is disadvantageous from the standpoint of cost since a palladium complex in an amount equal to or more than the theoretical amount is used though it is a method of higher atom economy from the standpoint of raw material. In addition, post treatment of the palladium complex after the reaction is troublesome, further, the yield is low. That is, it is not necessarily an advantageous method from the standpoint of industrial production.
As a process for producing a compound having an indole ring, there is known a process protecting a nitrogen atom constituting an indole ring with a benzenesulfonyl group, then, reacting it with an acrylic acid compound in the presence of a palladium catalyst (for example, Synthesis, 236 (1984)). This process, however, is a reaction limited to a compound in which a nitrogen atom constituting an indole ring is protected with a benzenesulfonyl group, and additionally, needs a use in excess amount of a relatively expensive re-oxidizer such as, for example, silver acetate and the like for obtaining an intended object in good yield.